   "Rename objects in ctx by given hash old-to-new."
   [ctx old-to-new]
   (let [objs (map old-to-new (objects ctx))
-	inz (set-of [(old-to-new g) m] [[g m] (incidence ctx)])]
+        inz (set-of [(old-to-new g) m] [[g m] (incidence ctx)])]
     (make-context-nc objs (attributes ctx) inz)))
 
 (defn rename-attributes
   "Rename attributes in ctx by given hash old-to-new."
   [ctx old-to-new]
   (let [atts (map old-to-new (attributes ctx))
-	inz (set-of [g (old-to-new m)] [[g m] (incidence ctx)])]
+        inz (set-of [g (old-to-new m)] [[g m] (incidence ctx)])]
     (make-context-nc (objects ctx) atts inz)))
 
 (defn make-context-from-matrix

  (if (not= (attributes ctx-1) (attributes ctx-2))
    (illegal-argument "Cannot do context subposition, since attribute sets are not equal."))
  (let [new-objs (union (set-of [g 1] [g (objects ctx-1)])
			(set-of [g 2] [g (objects ctx-2)]))
	new-inz  (union (set-of [[g 1] m] [[g m] (incidence ctx-1)])
			(set-of [[g 2] m] [[g m] (incidence ctx-2)]))]
    (make-context-nc new-objs (attributes ctx-1) new-inz)))

(defn context-transitive-closure

  "Returns tuple of number of objects, number of attributes and fill rate."
  [ctx]
  (let [obj-cnt (count (objects ctx)),
        att-cnt (count (attributes ctx)),
        inz-cnt (count (incidence ctx))]
    [obj-cnt, att-cnt, (if (or (zero? obj-cnt)
                               (zero? att-cnt))
                         Double/NaN
